Twitter update: "the request token for this page is invalid"

I am new, but I understand most things about the dashboard, and how it works. One feature of WordPress that I really wanted and understood from the start was, the automatic "push" out to Facebook and Twitter each time I post.

So I set up my dashboard to do both, and from day one, the Facebook one worked perfectly, and the Twitter one fails every time.

I then push the "Authorise connection with Twitter" button, which immediately takes me to an error page that says:

"Whoa there!

The request token for this page is invalid. It may have already been used, or expired because it is too old. Please go back to the site or application that sent you here and try again; it was probably just a mistake."

I've checked my settings on Twitter, and it shows that it allows WordPress - but, I can't get it to authorise from the WordPress side. The error message seemed pretty stupid the first time - "invalid", how could a token that had never been used aleady be "invalid"? Now, I've seen that message 22 times, once for each post.

How can I fix this? What do I have to do to get the WordPress app to REALISE that I've already told Twitter that it's OK for Word Press to push the message about the blog entry to it?

Please help, my Word Press experience WOULD have been 100% positive if it weren't for this irritating, unsolved issue - please someone tell me step by step what to do to "force" twitter and word press to play nicely together :-)